1. Field of the Invention
The present invention relates to a sealed battery cell, and to a manufacturing method for a sealed battery cell.
2. Description of Related Art
In a cylindrical sealed battery cell that is representative of a lithium secondary battery cell and so on, it is per se known to provide an anti-explosion mechanism between an electrode group and a top cover. The electrode group includes a positive electrode on which a positive electrode mixture is spread and a negative electrode on which a negative electrode mixture is spread wound together with the intervention of a separator.
With a sealed battery cell that uses an organic type solvent as electrolyte, when a high electrical current flows the electrolyte decomposes due to an overcharge state or a short circuited state of the positive terminal, gas is generated in the interior of the battery cell. Due to this gas that is generated, the pressure internal to the battery cell rises, and this can cause the battery to explode. An anti-explosion mechanism is a mechanism for preventing such explosion or the like of the battery cell due to elevated internal pressure.
The following construction is per se known as a prior art anti-explosion mechanism. An anti-explosion plate (i.e. a diaphragm) is disposed below the inner surface of the top cover (i.e. below its lower surface), and deforms along with elevation of the internal pressure, so that its central portion protrudes outwards towards the top cover. A lead attachment member (i.e. a connection plate) is provided upon the lower surface of this anti-explosion plate, and a connection lead is welded to the lower surface of the lead attachment member (connection plate). An insulating member is interposed between the lead attachment member and the anti-explosion plate, and the lead attachment member and the connection lead are connected together by ultrasonic welding. Furthermore, at the lower surface of the lead attachment member, the connection lead that is connected to a positive electrode collector member is welded.
With this type of construction, if the internal pressure rises, then the continuity between the positive electrode and the top cover is broken due to deformation of the anti-explosion plate, and/or the anti-explosion plate breaks (i.e. cleaves) so that the gas inside the battery cell is vented, and thereby explosion of the battery cell is prevented.
In Japanese Laid-Open Patent Publication Heisei 7-105933, there is disclosed a structure in which a lead attachment member is also endowed with a function of cleaving.